"Engineers are pests who want to know every detail and that's why I delve so deeply into this stuff," said Scicchitano, who thinks of himself as an expert in dietary supplements and praises them as the source of his vim, vigor and longevity.

Scicchitano is not alone.

Dietary supplements, numerous experts say, have long been held in high esteem by the American public. An estimated 150 million people nationwide take them, fueling a powerful $30 billion industry with potent political sway.

But just as there is a bright side to the industry -- its loyal consumer base -- there is a controversial element: unscrupulous operators, ex-cons and scammers who push questionable products into the marketplace, officials say.

In late 2011, 17 different supplement products containing DMAA, or dimethylamylamine, were pulled from military commissary shelves following five deaths and reports of serious injuries. Although Department of Defense officials said none of the deaths was caused by DMAA, the Food and Drug Administration warned supplement makers to halt production of DMAA-based supplements in 2012 and pressured USPlabs, the makers of DMAA-containing Jack3d, to destroy its $8 million inventory last year.

Critics blame the flood of questionable products on the law that deregulated the supplement industry, a measure that marks a major milestone this year. The Dietary Supplement Health and Education Act's 20th anniversary is in October.

In the years since the 1994 implementation of the act, which does not require proof of effectiveness or safety before a supplement can go on sale, the number of dietary aids has skyrocketed from 4,000 to an estimated 55,000 to 70,000.

More than five dozen federal warnings and recalls have been issued this year alone. Lawmakers have proposed measures for years to put more regulatory controls into force but almost all have been voted down as regulators chase a host of manufacturers, some peddling dangerous products in a largely unregulated marketplace.

In 2005, Long Island Internet proprietor Matthew Cahill was imprisoned for deliberately putting a pesticide into capsules and selling them over the Internet as a weight loss aid.

Since then, hundreds of other products have been cited for dangerous contents.

In March, the agency advised consumers not to purchase or use Vitaccino Coffee, a product promoted for weight loss and sold on various websites and in retail stores. The supplement contains sibutramine, a risky drug banned in October 2010 and known to substantially increase blood pressure.

Only a fraction -- fewer than 200 supplement products -- have ever been studied for side effects, said Dr. Paul Offit, who has challenged the use of unregulated dietary aids and whose hospital, the Children's Hospital of Philadelphia, eliminated supplements from its pediatric pharmacy last year.

Still, the FDA has no authority to require stringent product testing before a supplement hits the market. The supplement law allows products to be sold even without the type of testing required of over-the-counter drugs, Offit said.

"You consume a lot of this stuff at your own peril," said Offit, adding that a placebo effect has long been associated with supplements.

Many people who attribute their health to them, he said, would likely be just as healthy without dietary aids.

In defense of the supplement industry, Garden City lawyer Marc Ullman said there's no need to tighten government regulations.

As chairman of the legal advisory council for the Natural Products Foundation, a leading industry organization, Ullman said supplement makers are fully capable of policing themselves. The industry, he said, can weed out bad actors and deceptive practices.

He criticized the term "deregulated industry." Supplement makers, he said, are required to undergo routine FDA inspections. "This has been a requirement for years. I would call that regulation, wouldn't you?" Ullman said of federal manufacturing scrutiny, which has been required since 2008.

Scicchitano, meanwhile, takes a strong stand for supplements and says he isn't fazed by news of adulterated products or studies that find consuming supplements to be a fruitless effort.

He sees dietary aids as part of a healthy life, along with exercising and eating well. "My wife and I are very concerned about our health," he said. "Neither of us ever smoked. We exercise daily using our Gazelle Spring Master."

Scicchitano said vitamins A, B, C, D and E, saw palmetto and a slew of other supplements have helped him avoid cancer and other serious maladies.

Many doctors and policy-makers are concerned about an absence of laws barring supplement manufacturers with criminal backgrounds from entering the business. Known ex-cons have actually returned to the industry after serving time for supplement-related crimes.

Cahill, of Franklin Square, was imprisoned in 2005 for filling capsules with the pesticide DNP, then selling them over the Internet and through the U.S. Postal Service. He went back into the supplement business after 24 months behind bars.

He currently sells bodybuilding supplements from his Internet business, Designer Sports. In April, the FDA warned Cahill about lacing his workout powder, Craze, with a stimulant called Dendrobex, which the product's label claims is derived from chrysanthemums. Federal scientists say there is no such compound in the plant.

Federal records indicate that in the early 2000s Cahill posed as a professional in the gardening business to obtain the chemical 2,4-dinitrophenol, DNP, used on plants to regulate growth. It was developed in the 1930s as a weight-loss compound but caused blindness in people who took it. The FDA banned human use in 1938.

Cahill pleaded guilty to 11 counts that included "conspiracy to introduce adulterated and misbranded drugs into interstate commerce, specifically DNP."

Ullman said his client served his time and the act is behind him. There is no reason, he added, to link Cahill's past to his present.

"People serve their time and our society recognizes that," Ullman said. "When you've paid your debt, you are allowed to go back into the world without wearing a scarlet letter."

Dr. Daniel Fabricant, director of the FDA's dietary supplement programs at the agency's Center for Food Safety and Applied Nutrition, confirmed there are no restrictions on ex-cons from entering the supplement business.

Even former prisoners who were never in the supplement business but found guilty of scamming people in other ways are also free to make dietary aids once released.

Jordan Belfort, 51, the so-called Wolf of Wall Street, freed in 2006 after 22 months of incarceration for securities fraud, was barred by law from returning to the financial industry. But he opened a Long Island supplement business after his release. The business is now defunct.

If the FDA becomes aware of a problem with a supplement or how it's made, the agency can request that manufacturers voluntarily recall it. The agency routinely issues warnings about dicey products. Last year, 70 percent of inspected companies had manufacturing lapses, ranging from an absence of recipes for vitamins to rodent infestations and improperly functioning machinery.

While most vitamins and supplements are not harmful -- and at least one vitamin brand was credited with an 8 percent reduction in cancer among men over 50 -- the industry is beset by repeated recalls, manufacturing problems and adverse reactions caused by tainted products, experts and officials say.

"I find that most people who take vitamins and supplements are usually well-informed and well-read. I am, anyway. And I believe people who take vitamins and supplements are rigorous in their analysis of their usage."